Aggregate

The ability of proteoglycan to contribute to an even larger molecular structure by combining with hyaluronan originally was described by Hardingham and Muir.

Those authors elaborated on the dissociation and association experiments of Sajdera and Hascall to establish the mechanism of formation of the larger molecule, termed proteoglycan aggregate. Much attention has been given to the degree of aggregate formation in various tissues and in various pathologic conditions .

Clearly, the ability of the proteoglycan molecule to form aggregates of great molecular size amplifies its physiological functional properties as the “pump” of the articular cartilage system.

Lohmander has noted that the molecular weight of aggregate is 100,000,000 to 200,000,000 Da, whereas for a common protein, such as insulin, the molecular weight is only 6,000 Da.

Because of its much greater size, the aggregate formed will impose even greater fixation of the proteoglycan molecules, locking them more securely within the interstices of the collagen framework of the tissue and ensuring fixation of the negative charges needed to maintain swelling pressure for expansion of the articular cartilage matrix.